Lucia

Tutorial: Username and password auth in Nuxt

Before starting, make sure you've set up your database and middleware as described in the Getting started page.

An example project based on this tutorial is also available. You can clone the example locally or open it in StackBlitz.

npx degit https://github.com/lucia-auth/examples/tree/v3/nuxt/username-and-password

Update database

Add a username and hashed_password column to your user table.

column type attributes
username string unique
hashed_password string

Create a DatabaseUserAttributes interface in the module declaration and add your database columns. By default, Lucia will not expose any database columns to the User type. To add a username field to it, use the getUserAttributes() option.

// server/utils/auth.ts
import { Lucia } from "lucia";

export const lucia = new Lucia(adapter, {
	sessionCookie: {
		attributes: {
			secure: !import.meta.dev
		}
	},
	getUserAttributes: (attributes) => {
		return {
			// attributes has the type of DatabaseUserAttributes
			username: attributes.username
		};
	}
});

declare module "lucia" {
	interface Register {
		Lucia: typeof lucia;
		DatabaseUserAttributes: DatabaseUserAttributes;
	}
}

interface DatabaseUserAttributes {
	username: string;
}

Sign up user

Create pages/signup.nuxt and set up a basic form.

<!--pages/signup.vue-->
<script lang="ts" setup>
async function signup(e: Event) {
	const result = await useFetch("/api/signup", {
		method: "POST",
		body: new FormData(e.target as HTMLFormElement)
	});
	if (!result.error.value) {
		await navigateTo("/");
	}
}
</script>

<template>
	<h1>Create an account</h1>
	<form method="post" action="/api/login" @submit.prevent="signup">
		<label htmlFor="username">Username</label>
		<input name="username" id="username" />
		<br />
		<label htmlFor="password">Password</label>
		<input type="password" name="password" id="password" />
		<br />
		<button>Continue</button>
	</form>
</template>

Create an API route in server/api/signup.post.ts. First, do a very basic input validation. Hash the password, generate a new user ID, and create a new user. If successful, create a new session with Lucia.createSession() and set a new session cookie.

// server/api/signup.post.ts
import { Argon2id } from "oslo/password";
import { generateId } from "lucia";
import { SqliteError } from "better-sqlite3";

export default eventHandler(async (event) => {
	const formData = await readFormData(event);
	const username = formData.get("username");
	if (
		typeof username !== "string" ||
		username.length < 3 ||
		username.length > 31 ||
		!/^[a-z0-9_-]+$/.test(username)
	) {
		throw createError({
			message: "Invalid username",
			statusCode: 400
		});
	}
	const password = formData.get("password");
	if (typeof password !== "string" || password.length < 6 || password.length > 255) {
		throw createError({
			message: "Invalid password",
			statusCode: 400
		});
	}

	const hashedPassword = await new Argon2id().hash(password);
	const userId = generateId(15);

	// TODO: check if username is already used
	await db.table("user").insert({
		id: userId,
		username: username,
		hashed_password: hashedPassword
	});

	const session = await lucia.createSession(userId, {});
	appendHeader(event, "Set-Cookie", lucia.createSessionCookie(session.id).serialize());
});

We recommend using Argon2id, but Oslo also provides Scrypt and Bcrypt. These only work in Node.js. If you're planning to deploy your project to a non-Node.js runtime, use Scrypt provided by lucia. This is a pure JS implementation but 2~3 times slower. For Bun, use Bun.password.

import { Scrypt } from "lucia";

new Scrypt().hash(password);

If you're using Bcrypt, set the maximum password length to 64 bytes.

const length = new TextEncoder().encode(password).length;

Sign in user

Create pages/login.vue and set up a basic form.

<!--pages/login.vue-->
<script lang="ts" setup>
async function login(e: Event) {
	const result = await useFetch("/api/login", {
		method: "POST",
		body: new FormData(e.target as HTMLFormElement)
	});
	if (!result.error.value) {
		await navigateTo("/");
	}
}
</script>

<template>
	<h1>Sign in</h1>
	<form method="post" action="/api/login" @submit.prevent="login">
		<label htmlFor="username">Username</label>
		<input name="username" id="username" />
		<br />
		<label htmlFor="password">Password</label>
		<input type="password" name="password" id="password" />
		<br />
		<button>Continue</button>
	</form>
</template>

Create an API route as server/api/login.post.ts. First, do a very basic input validation. Get the user with the username and verify the password. If successful, create a new session with Lucia.createSession() and set a new session cookie.

// server/api/login.post.ts
import { Argon2id } from "oslo/password";

export default eventHandler(async (event) => {
	const formData = await readFormData(event);
	const username = formData.get("username");
	if (
		typeof username !== "string" ||
		username.length < 3 ||
		username.length > 31 ||
		!/^[a-z0-9_-]+$/.test(username)
	) {
		throw createError({
			message: "Invalid username",
			statusCode: 400
		});
	}
	const password = formData.get("password");
	if (typeof password !== "string" || password.length < 6 || password.length > 255) {
		throw createError({
			message: "Invalid password",
			statusCode: 400
		});
	}

	const existingUser = await db
		.table("username")
		.where("username", "=", username.toLowerCase())
		.get();
	if (!existingUser) {
		// NOTE:
		// Returning immediately allows malicious actors to figure out valid usernames from response times,
		// allowing them to only focus on guessing passwords in brute-force attacks.
		// As a preventive measure, you may want to hash passwords even for invalid usernames.
		// However, valid usernames can be already be revealed with the signup page among other methods.
		// It will also be much more resource intensive.
		// Since protecting against this is none-trivial,
		// it is crucial your implementation is protected against brute-force attacks with login throttling etc.
		// If usernames are public, you may outright tell the user that the username is invalid.
		throw createError({
			message: "Incorrect username or password",
			statusCode: 400
		});
	}

	const validPassword = await new Argon2id().verify(existingUser.password, password);
	if (!validPassword) {
		throw createError({
			message: "Incorrect username or password",
			statusCode: 400
		});
	}

	const session = await lucia.createSession(existingUser.id, {});
	appendHeader(event, "Set-Cookie", lucia.createSessionCookie(session.id).serialize());
});

Validate requests

You can validate requests by checking event.context.user. The field user.username is available since we defined the getUserAttributes() option. You can protect pages, such as /, by redirecting unauthenticated users to the login page.

export default defineEventHandler((event) => {
	if (event.context.user) {
		const username = event.context.user.username;
	}
	// ...
});

Get user in the client

Create an API route in server/api/user.get.ts. This will just return the current user.

// server/api/user.get.ts
export default defineEventHandler((event) => {
	return event.context.user;
});

Create a composable useUser() in composables/auth.ts.

// composables/auth.ts
import type { User } from "lucia";

export const useUser = () => {
	const user = useState<User | null>("user", () => null);
	return user;
};

Then, create a global middleware in middleware/auth.global.ts to populate it.

// middleware/auth.global.ts
export default defineNuxtRouteMiddleware(async () => {
	const user = useUser();
	user.value = await $fetch("/api/user");
});

You can now use useUser() client side to get the current user.

<script lang="ts" setup>
const user = useUser();
</script>

Sign out

Sign out users by invalidating their session with Lucia.invalidateSession(). Make sure to remove their session cookie by setting a blank session cookie created with Lucia.createBlankSessionCookie().

// server/api/logout.post.ts
export default eventHandler(async (event) => {
	if (!event.context.session) {
		throw createError({
			statusCode: 403
		});
	}
	await lucia.invalidateSession(event.context.session.id);
	appendHeader(event, "Set-Cookie", lucia.createBlankSessionCookie().serialize());
});

<script lang="ts" setup>
async function logout() {
	await useFetch("/api/logout", {
		method: "POST"
	});
	navigateTo("/login");
}
</script>

<template>
	<form @submit.prevent="logout">
		<button>Sign out</button>
	</form>
</template>